SAO PAULO, April 24 (Reuters) - A JBS SA poultry plant in southern Brazil was hit by an outbreak of COVID-19, according to labor prosecutors, marking the first large-scale infection at a Brazilian meat plant.

The respiratory illness caused by the novel coronavirus affected 20 workers at the meat-processing facility in the town of Passo Fundo, in the state of Rio Grande do Sul, according to a representative from the state’s labor prosecutor’s office on Friday.

The plant was shut Friday afternoon as part of an ongoing investigation by the prosecutors. It follows several other outbreaks at meat-processing facilities in the United States in recent weeks, including at some JBS-owned plants.

A source close to the company said earlier that 12 workers at the plant were infected.

In a statement responding to queries about the Passo Fundo plant, JBS said it follows guidelines from local health authorities and keeps strict controls at its processing plants, distribution centers and offices to avoid contamination from the novel coronavirus.

It declined to comment on the cases of COVID-19 affecting its employees and said nothing specifically about the outbreak at the Passo Fundo plant, which employs 2,600 workers.

The labor prosecutor’s office confirmed that it found at least seven cases when its probe began a few days ago, and said the tally has since risen to 20.

Reuters could not reach the Passo Fundo health department or city officials for comment.

Brazilian news website UOL cited the department as saying that some 78 JBS employees had been removed from work for showing flu symptoms.

The labor prosecutor’s office, which on Saturday filed a civil lawsuit against JBS seeking damages, said the meat processor’s failure to follow health authority guidelines had triggered its investigation.

The company, which earlier noted that food production is considered one of the essential activities authorized to operate amid coronavirus lockdowns, denied any breach of health guidelines at the plant and said Passo Fundo would resume operations soon.

The settlement JBS refused to sign would have been similar to an agreement between food processor Companhia Minuano de Alimentos, also in Rio Grande do Sul. Minuano confirmed removal of 750 employees while 16 employees tested positive for COVID-19, out of a total of 2,051, according to the prosecutors. (Reporting by Ana Mano; Editing by Christian Plumb, Jonathan Oatis and Leslie Adler)